By Remark REF , rather than employing the optimization approach, to numerically solve Problem REF , we propose to regularize and approximate the inverse problem by truncating the high frequency components of the solution to (REF ).
This idea was introduced in [1]}. Then, it was successfully used in many projects of our research group; see e.g. [2]}, [3]}, [4]}. Details will be given in the next section.
